One of the striking characteristics of fundamental biological processes, such as genetic inheritance, development and primary metabolism, is the limited amount of variation in the molecules involved. Natural selective pressures act strongly on these core processes and individuals carrying mutations and producing slightly sub-optimal versions of key molecules do not survive long term. However, it has also become apparent that there are different selective pressures on different parts of proteins so that some regions of a particular enzyme are highly conserved across different species while others are more variable. Using publicly available software along with collated amino acid sequence data, one can "line up" particular enzyme sequences (such as trypsin) and discover that the highly conserved regions are those that contain amino acids located at the active site. Furthermore, different software can be used to exploit the variable regions of amino acid sequence to reconstruct the evolutionary pathway (phylogeny) of the species used. If, on the other hand, one examines biological molecules that act in processes less directly critical for survival, one finds tremendous diversity, much of which has been exploited by humans. Among the examples given are antibiotics produced by some microorganisms, clinical and recreational drugs, dyes and compounds used in the fight against cancer. It is clear that the biological world contains large numbers of molecules that can be valuable commercially and in health care and this is one obvious reason to protect the planet's biodiversity. (Contains 11 figures.)